The present invention relates to an apparatus for the suspension of an aircraft turbo-fan engine cowling to a supporting structure, especially for a high by-pass ratio engine of high thrust rating.
Particularly these large engines exhibit significant deflections and distortions due to a combination of engine mount reactive forces and external moments applied by aerodynamic loads on the engine inlet ducting. The primary deflection experienced during operation of the engine is caused by the bending moment under high power. The high thrust load is a summation of internal forces, the resultant of which acts along the centerline of the engine. The engine mounts react this force back to the supporting structure. Due to other installation requirements, this reaction force is above the centerline of the engine, resulting in the afore-mentioned bending moment.
Basic aircraft design dictates the use of thin walled engine cases, resulting in significant deflections which adversely affect the performance of the engine. The efficiency of an engine requires close clearances between the rotors and the engine cases. Deflections of the cases result in contact between the rotors and the engine cases and a loss of efficiency due to the resulting blade rubbing.
The cowling required for securing the engine basically forms a tubular member around the engine that can be utilized to reduce engine case deflections. The utilization of cowling in this manner is called Cowl Load-Sharing (CLS). Installation, removal and servicing of the engine requires the cowling to be in two halves. When opened these are suspended from hinges attached to a suspension apparatus. When closed during engine operation, these halves are suitably tied together, forming the tubular member that is being utilized to reinforce the engine and reduce engine case deflections.
The currently used apparatus for the suspension of an aircraft jet engine includes a flexmount unit secured to the supporting structure and a pylon attached underneath the flexmount unit and to which the engine cowling is suspended. In this prior art suspension apparatus, the cowling is suspended by attachment means on its front and rear parts. The flexmount unit is caused to bend under the weight and thrust of the engine during operation and as a result from the method of suspension of the cowling cowl load sharing cannot be achieved and detrimental engine case deflections cannot be avoided during engine operation, resulting in the aforementioned blade rubbing and the consequent loss of efficiency. There was thus a problem to be solved in order obviate the above drawbacks.